In preoperative patients with locoregional solid malignancies serum levels of alpha1-acid glycoprotein and haptoglobin correlated inversely and alpha2HS-glycoprotein correlated directly with both in vivo (delayed hypersensitivity to DNCB) and in vitro (lymphocyte reactivity to PHA) parameters of cellular immunity. In patients with head and neck squamous carcinoma, these glycoproteins correlated with clinical tumor stage and in patients with NPC also with antibody titers of EB virus. T cell subpopulations (T micron and T gamma) were graphically identified and quantitated by cytofluorographic analysis. The results correlated with those obtained by ligh microscope counting. The alpha1 polypeptide of thymosin fraction 5 when added in vitro to T lymphocytes from cancer patients was associated with a change to normal range of T micron and T gamma cells when the levels of these cells exceeded the range in normals. Several but not all subunits of alpha1 also had this effect in vitro on these T lymphocyte subpopulations.